Molecular and Virulence Characterization of Newcastle Disease Virus in Fowls and Pigeons From Jammu, India

Abstract

Occurrence of Newcastle disease (ND) and characterization of the Avian Paramyxovirus-1 (APMV-1) amongst backyard fowls (Gallus gallus domesticus) and pigeon (Columba livia domestica) was studied. ND was suspected in two fowl flocks (100% morbidity, 86% mortality) and six pigeon flocks (21.68% morbidity, 14.16% mortality) with respiratory and/or enteric clinical signs in fowls and predominantly neurological signs in pigeons was observed. Cloacal swabs, tissue lysates or infected allantoic fluid could haemagglutinate (HA) chicken erythrocytes and pigeon convalescent serum inhibited haemagglutination (antibody titres >1/16). A 534 bp product was amplified from clinical samples and infected allantoic fluids by Reverse Transcriptase PCR (RT-PCR) targeting a partial Fusion protein gene including its cleavage site. The fowl and pigeon isolate was found to be velogenic and lentogenic respectively by virulence characterization. Fowl isolate grown in chicken embryonated eggs (CEE) showed 10-8.68 Embryo Infectious Dose (EID50) with a Mean Death Time (MDT) of 51.43 h and the Intra-Cerebral Pathogenicity Index (ICPI) in day-old chicks was 1.51. Pigeon isolate had corresponding values of 10-7.20 EID50, MDT of 92.00 h and ICPI of 0.43. Deduced amino acid sequence at Fusion protein cleavage site showed 112R-R-R-K-R*F117 velogenic motif for the fowl isolate and 112G-R-Q-G-R*L117 lentogenic motif for the pigeon isolate. Both isolates were found to be 84.1% related phylogenetically, while fowl isolate clustered with genotype XIII, the pigeon isolate clustered with genotype II and vaccine strains of APMV-1. This is the first instance of APMV-1 characterization in the region with the possibility of a vaccine spill over in pigeons.